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Corrosion increases the nominal stress of reinforcing bars and accelerates the fatigue crack propagation. The stress redistribution induced by bond degradation between concrete and rebars makes the fatigue life prediction of reinforced concrete (RC) structures more complicated. This paper proposes a crack propagation-based fatigue life prediction method for corroded RC beams incorporating fatigue damage of concrete, fatigue bond degradation, and pitting corrosion. The fatigue damage of concrete is modeled based on plastic strain analysis. For the fatigue-worsened bond degradation between concrete and corroded rebars, a novel strain-incompatibility analysis method is developed to quantify the slip of reinforcements in concrete. The fatigue crack propagation parameters of rebars and the corrosion pit-induced stress concentration are experimentally obtained. The stress intensity for the fatigue crack at the corrosion pit root is calculated by an asymptotic interpolation method. Then, the fatigue failure analysis of corroded RC beams is performed, where the reinforcement fracture, concrete crush, and bond degradation-induced anchorage failure at beam ends are checked. The proposed method is verified by the test data. The effects of bond degradation and concrete damage on the fatigue life prediction are analyzed and discussed. The proposed method for fatigue life prediction gives a reasonable estimate of the service life of corroded RC beams. [ABSTRACT FROM AUTHOR]

Highlights • Fatigue loading tests on corroded RC beams are performed. • Load-deflection, fatigue crack of concrete, and failure modes are discussed. • A developed flexural stiffness deterioration model under fatigue is proposed. • Theoretical predictions agree well with the experimental observations. Abstract Corrosion of reinforcing bars accelerates the fatigue damage accumulation and significantly reduces the fatigue life of aging reinforced concrete (RC) bridges. This paper experimentally investigates the effects of corrosion on the fatigue behavior of reinforced concrete beams. An accelerated corrosion test is conducted in the laboratory conditions to obtain various corroded beam specimens. The initial crack width and the crack distribution are discussed. Based on the fatigue loading test, the load-deflection, fatigue crack propagation of concrete, fatigue life and the failure modes of RC beams after different fatigue cycles are investigated. Following that, a developed flexural stiffness calculation model for the corroded beams after fatigue is proposed. This model includes the effects of fatigue, corrosion-induced cracking and fatigue modulus degradation of concrete and other influential factors. The proposed method is validated with the experimental observations from various corroded RC beams of the current paper and available in open literature. [ABSTRACT FROM AUTHOR]

An experimental study is conducted in this paper to investigate the effect of corrosion and corrosion-induced cracks on the bond behavior between steel bars and concrete. An accelerated corrosion test was used to corrode the steel bars embedded in concrete specimens under laboratory condition. Two series of pull-out tests were designed. Pull-out tests on the specimens with plain and deformed reinforcing bars are performed. The bond behavior of the two types of steel bar specimens including the ultimate bond strength, bond-slip relationships for different corrosion levels are discussed. An empirical bond degradation model is proposed combining a wide range of experimental data available in the literatures. The other pull-out tests on the bonding specimens with interior strain gauges are conducted and the bond stress at various positions are derived based on the observed reinforcement strains. The experimental results show that the corrosion influence on bond strength can be ignored when the corrosion loss is less than 2.4%. The bond behavior between smooth bar and concrete is more sensitive to the corrosion than that of specimen with deformed bar. The selection of steel bars is also an alternative way to improve the bond behavior especially for the deformed bar specimens. The distribution of bond stress is more uniform for the specimen with a large corrosion-induced crack width. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the effects of corrosion-induced cracking damage on the static behavior of corroded reinforced concrete arch ribs. Four circular reinforced concrete arches including an uncorroded arch rib and three corroded arch ribs are designed and made in laboratory conditions. The initial crack distribution and crack width are discussed by accelerated corrosion test observations. Based on a five-loading static test, the crack propagation, the load–displacement response, the ultimate load bearing capacity and the failure modes of arch ribs are also discussed. Following this, a developed calculation model considering the effect of corrosion damage is used to assess the capacity of the arch ribs. Experimental data are used to validate the proposed method and reasonable agreement is observed between theoretical predictions and experimental results. [ABSTRACT FROM AUTHOR]

A new crack growth-based corrosion fatigue life prediction method for aging reinforced concrete beam is proposed in this paper. The proposed method couples the corrosion growth kinetics and fatigue crack growth kinetics together. The relationship between corrosion damage morphology and corrosion loss is investigated by the experimental results. A phenomenological model is proposed to obtain the stress concentration factor model under different corrosion loss conditions. Following this, the developed model is integrated with an asymptotic method to calculate the stress intensity factor for the crack at corrosion pit roots. The fatigue life is predicted by the integration of the fatigue crack growth rate curve from the equivalent initial flaw size to the critical length. Probabilistic analysis methodology is proposed to consider various sources of uncertainties for the fatigue life prediction. Fatigue life prediction results are validated with experimental observations for various corroded steel bars and beams available in the literatures. [ABSTRACT FROM AUTHOR]

A general methodology for probabilistic corrosion analysis of reinforcing bar in RC bridges is proposed in this paper. Uncertainties due to limited number of experimental data, incomplete inspection information, as well as the intrinsic randomness of random variables affect the prognostics of corrosion damage. The proposed study includes both fuzziness and randomness to consider different types of uncertainties. First, the chloride-induced corrosion initiation and propagation model are developed for reinforcement in RC bridge. The relationship between the area corrosion rate and the yield strength degradation is proposed on the basis of experimental investigation from accelerated corrosion testing. Following this, the randomness and fuzziness are included using fuzzy random variables to consider the uncertainties of the degradation under corrosive environments. The probabilistic modeling of the mean and the SD of reinforcement yield strength is discussed in detail. Finally, the proposed methodology is illustrated and validated with field measurements of corroded reinforcement in RC beams from a 34-year-old decommissioned RC bridge. The predicted results agree well with experimental values. [ABSTRACT FROM AUTHOR]

Shear strength is a widely investigated parameter for reinforced concrete structures. The corrosion of reinforcement results in shear strength reduction. Corrosion has become one of the main deterioration factors in reinforced concrete beam. This paper proposes a shear strength model for beams with inclined bars based on a limit equilibrium method. The proposed model can be applied to both corroded and uncorroded reinforced concrete beams. Besides the tensile strength of longitudinal steel bars, the shear capacity provided by the concrete on the top of the diagonal crack, the tensile force of the shear steel at the diagonal crack, the degradation of the cross-sectional area and strength of the reinforcements induced by corrosion are all considered. An experimental work on two groups accelerated corroded beams was performed. Good agreements were found between the proposed theoretical predictions and experimental observations. [ABSTRACT FROM AUTHOR]

A systematic framework is proposed to quantify hybrid uncertainties (i.e., aleatory and epistemic uncertainty) for the probabilistic prediction of corrosion damage in aging reinforced concrete (RC) bridges when the initial statistical parameters of variable are not available, sparse or cannot be accurately obtained. The key idea is to use a likelihood-based approach to calculate the probability distribution function (PDF) of the variable described by sparse data and an entropy-based transformation method to obtain the PDF of variable described by expert-based information. Following this, a hybrid description of uncertainties is proposed using the marginal integration. The uncertainty quantification of important factors on corrosion initiation and propagation are discussed, and a time-variant corrosion cracking model is developed. The proposed methodology is illustrated and demonstrated by a numerical example of corrosion damage prediction of an existing RC bridge. The prediction results of corrosion damage agree well with the experimental observations. [ABSTRACT FROM AUTHOR]

In the design of frame-core tube structures, the method for adjusting the frame bearing capacity and stiffness to ensure the structure as a dual system is a critical issue. This study investigates the effects of frame shear distribution ratio, frame bearing capacity, and column pattern on the seismic performance of concrete-filled steel tubular frame to reinforced concrete core tube structures (CFRCTs). Time-history and seismic fragility analyses on eight representative models are performed and the distribution pattern of inter-story drift ratios, structural damage modes, and collapse safety margins are compared. The study results show that CFRCTs possess superior seismic performance (with a collapse margin ratio > 9.3) compared to the structures with reinforced concrete columns and the collapse margin ratio continuously increases from 9.3 to 11.2 with increasing frame stiffness. Enhancing the frame bearing capacity mitigates the frame damage, while improving slightly on structure's collapse resistance (< 0.1 %). Without adjusting the frame for the second fortification line, damage to the column is not serious and the frame can still effectively withstand the increased shear force transmitted from the core tube during an extremely severe earthquake. The frame experiences more shear force and damage as the frame shear distribution ratio increases; while the core tube damage is effectively alleviated. Due to the redistribution of internal forces, the distribution pattern of inter-story drift ratios under the collapse state is markedly distinct from that under the elastic stage and severe earthquakes. Based on the analysis, design suggestions considering both collapse resistance and economic efficiency are proposed for CFRCTs. • The seismic behavior of concrete-filled steel tubular frame to reinforced concrete core tube structures is investigated. • The working mechanism of the CFST frame as the second fortification line is analyzed. • Design suggestions considering the balance between collapse resistance and economic efficiency are proposed for CFRCTs. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study conducted to characterize the effect of corrosion and sustained load on structural behavior of reinforced concrete (RC) beam. The effects of loading level on corrosion of reinforcing steel, the flexural deflection and residual loading capacity of the test beams were investigated. In the first scenario, two non-corroded beams were tested to determine the maximum load levels that were required by the beams to reach their deflection limits and that were also tested for the sustained levels of the applied loads. For the second experiment, the corrosion was accelerated through the application of external direct current whilst the beams were under the load equivalent to 0%, 50%, 65% and 80% of the ultimate load. The results indicate that load levels have a significant effect on the rise of steel corrosion level, the decrease of flexural stiffness and the degradation of flexural capacity. The mechanical properties like the strength and ductility are significantly impaired due to simultaneous effect of loading and corrosion in comparison to the effect of the single parameter at a time. Considering the corrosion situation of different position of steel bar, the formula of the ratios of the different position of steel bar corresponding with different sustained loading levels was given. An equation was deduced to calculate the flexural stiffness of corroded reinforced concrete and can be served as a reference for deflection calculation of corroded reinforced concrete beams. [ABSTRACT FROM AUTHOR]

An experimental study is proposed to investigate the shear behavior of corroded reinforced concrete (RC) beams with stirrups and inclined bars. The proposed study aims to address the effects of corrosion in the two types of shear reinforcement on the shear capacity deterioration of RC beams with low shear span-to-effective depth ratio. The accelerated corrosion test is employed to obtain different corrosion levels in stirrups and inclined bars in fourteen RC beams. The corrosion-induced concrete cracking and section damage is discussed in detail. The shear behavior including load-deformation response, residual shear strength, diagonal cracking and failure mode is presented. The shear strength of beams is predicted by a modified ACI approach considering the corrosion loss of shear reinforcement and concrete section damage. It is observed that the slight corrosion loss less than 10% in stirrups and inclined bars has little effect on the degradation of shear behavior. The severe corrosion of stirrups and inclined bars, and the accompanied concrete section damage decreases the shear strength and stiffness significantly. Corrosion of stirrups and inclined bars does not change the shear compression failure mode of beams. Severe corrosion does reduce the number of cracks in beams and lead to early rupture of shear reinforcement. [ABSTRACT FROM AUTHOR]